PHYSIOLOGY AND MORPHOLOGY OF CALIFORNIA HEPATIC^ 13 



In his studies upon Lofhocolea hidentata. Cavers ' found that 

 the tissues of the gametophyte are entirely free from hyphae, 

 but the rhizoids which grow out in tufts from the bases of the 

 amphigastria penetrate the substratum of rotten wood and there 

 become profusely branched like the haustoria of many fungi. 

 This, he considers, enables the liverwort to assume a more or 

 less saprophytic existence. He has not however shown that the 

 plant actually does adapt itself to this mode of life, nor does it 

 appear that we can assume the branching of the rhizoids as due 

 to anything other than contact stimulus. Peirce and Randolph ^ 

 have demonstrated that in the case of certain attached fresh- 

 water algae and in many marine forms the development of a 

 holdfast is directly and wholly the result of contact stimulus. 

 The complexity and extent of the holdfast were found to vary 

 with the degree of roughness of the surface of the substratum ; 

 young plants grown on ground glass developing much more 

 elaborate holdfasts than similar plants grown on smooth glass 

 while those grown in dust-free water developed no holdfasts at all. 



In Knop's solution the writer now has plants of Fossomhronia^ 

 Crypioviiirtuin and other liverworts growing that were removed 

 from a normal soil substratum some months ago. Still attached 

 to these plants are some of the old rhizoids which are all more 

 or less gnarled and modified, some exhibiting short lateral proc- 

 esses. Since placing the plants in Knop's solution a great 

 number of rhizoids have developed and in every instance they 

 are perfectly straight and unmodified and much more delicate 

 in structure than those that had grown while the plants were in 

 their normal habitat. We have here exactly the same behavior 

 exhibited by the secondary roots and root-hairs of higher plants. 

 If, as some botanists maintain, the rhizoids of bryophytes are 

 simply organs of attachment is it not probable that, as in the 

 case of certain algee, these branches are due to the stimulus 

 afforded by contact? 



Aside from Aneura and Fossonibronia the writer has observed 

 branching rhizoids in Ccphalozia biaispidata, due probably to 



' Loc. cit., p. 32. 



^Peirce and Randolph, 1905: Studies of Irritability in Algae. Botanical 

 Gazette, 40- pp. 321-350. 



